11:45 AM - 12:00 PM
[PEM10-10] Mid-latitude Electric Field Response during Isolated Substorms: Effects of SCW Location, Shielding, and Aurora Activity
Keywords:substorm, M-I coupling, midlatitude
This study examines the mid-latitude electric field response to isolated substorms, with a focus on the influence of the Substorm Current Wedge (SCW) R1/R2 type currents, their spatial distribution, and their association with auroral activity.
The SCW characterizes the current system during substorms. The high-latitude electric field associated with the SCW penetrates toward mid- and low-latitudes. Prior studies have shown that the penetration electric field intensifies as the region-1 (R1) SCW increases, while the region-2 (R2) SCW tends to shield this electric field. Although many case studies have been performed, the statistical properties of the penetration electric field remain unclear, especially concerning the spatial distribution of the SCW. In this study, we examine the shielding effect and statistically analyze its impact on the mid-latitude electric field for substorms that occurred between 2010 and 2013 by:
• Estimating the temporal evolution of the SCW structure via the north-south and east-west ground magnetic field components from MAGDAS and SuperMAG.
• Evaluating the shielding effect through the R1/R2 SCW magnitude using AMPARE.
• Investigating the correlation between the SCW characteristics and the electric field's direction and magnitude, measured by Kyushu University’s FM-CW radar at mid-latitude.
The results of these analyses indicate that the dominant R1 SCW correlates with a westward electric field in the center of the SCW and an eastward electric field on the outside. The intensity of these fields varies with the substorm's scale. Moreover, when the R2 SCW's magnitude is equal to or exceeds that of R1, the resultant electric fields are either shielded or overshielded, leading to reduced magnitude or reversed direction. This emphasizes the significance of the R2 SCW's strength and the SCW's positioning in determining the penetration electric field's behavior.
Furthermore, mid-latitude electric fields were found to fluctuate on shorter time scales than AE and mid-latitude magnetic fields. By correlating these variations with auroral images from THEMIS in Alaska and OMTI in Paratunka and Magadan, we found a synchronous relationship between electric field variations and auroral brightening. This emphasizes the dynamic interaction between auroral activities and mid-latitude electric field variations, enhancing our comprehension of magnetosphere-ionosphere dynamics during substorms.
The SCW characterizes the current system during substorms. The high-latitude electric field associated with the SCW penetrates toward mid- and low-latitudes. Prior studies have shown that the penetration electric field intensifies as the region-1 (R1) SCW increases, while the region-2 (R2) SCW tends to shield this electric field. Although many case studies have been performed, the statistical properties of the penetration electric field remain unclear, especially concerning the spatial distribution of the SCW. In this study, we examine the shielding effect and statistically analyze its impact on the mid-latitude electric field for substorms that occurred between 2010 and 2013 by:
• Estimating the temporal evolution of the SCW structure via the north-south and east-west ground magnetic field components from MAGDAS and SuperMAG.
• Evaluating the shielding effect through the R1/R2 SCW magnitude using AMPARE.
• Investigating the correlation between the SCW characteristics and the electric field's direction and magnitude, measured by Kyushu University’s FM-CW radar at mid-latitude.
The results of these analyses indicate that the dominant R1 SCW correlates with a westward electric field in the center of the SCW and an eastward electric field on the outside. The intensity of these fields varies with the substorm's scale. Moreover, when the R2 SCW's magnitude is equal to or exceeds that of R1, the resultant electric fields are either shielded or overshielded, leading to reduced magnitude or reversed direction. This emphasizes the significance of the R2 SCW's strength and the SCW's positioning in determining the penetration electric field's behavior.
Furthermore, mid-latitude electric fields were found to fluctuate on shorter time scales than AE and mid-latitude magnetic fields. By correlating these variations with auroral images from THEMIS in Alaska and OMTI in Paratunka and Magadan, we found a synchronous relationship between electric field variations and auroral brightening. This emphasizes the dynamic interaction between auroral activities and mid-latitude electric field variations, enhancing our comprehension of magnetosphere-ionosphere dynamics during substorms.